Do I share the same intellectual abilities as my parents? It’s interesting to think about? I go to each of my parents in different situations, they both have individual strengths and we have shared talents and interests but is that due to genetics or the environment I was brought up in.
The major contributor to the nature argument was Francis Galton in his 1869 book, Hereditary Genius: Its Laws and Consequences (Galton, 2006). Galton suggested that gifted individuals tended to come from families which had other gifted individuals. He went on to analyze biographical dictionaries and became convinced that talent was genetic. Galton was convinced that it was
“Quite practicable to produce a high gifted race of men by judicious marriages during several consecutive generations…intelligence must be bred, not trained” (Galton, 2006).
This theory became known as eugenics. Galton wanted to speed up the process of natural selection, stating that:
“What Nature does blindly, slowly, and ruthlessly, man may do providently, quickly, and kindly”.
Such arguments have had massive social consequences and have been used to support apartheid policies and sterilization programs.
In the 1920’s heyday of eugenic IQ testing there was no evidence for how inheritable IQ is; today that is no longer the case. The inherit-ability of IQ is now a hypothesis that has been tested on twins and adopters often showing a substantial amount of inherit-ability. Experiments though-out America in 1979 showed a 76% correlation when testing identical twins that had been reared apart (Ridley, 1999).
Inherit-ability however is not a pure measure of genetic inheritance as environmental factors including the pre and post natal environments would need to be included.
Inherit-ability estimates based on comparing mono-zygotic (identical) twins reared together is likely to overestimate the genetic component because mono-zygotic twins share similar environments, both in the womb and out (Shallow, 2009).
Twin studies cannot be generalized to the population as a whole. Twins are more susceptible to prenatal trauma leading to retardation. The inclusion of retarded cases could increase the correlation in intelligence test scores.
The other side of the agreement is nurture and the experiences our environment brings.
“Give me a dozen healthy infants & my own specific world to bring them up in, & I’ll guarantee to take any one at random & train him to become any type of specialist I might select – doctor, lawyer, artist, merchant, chef & yes, even beggar & thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.” (Gross, 2002).
This is a quote from behaviourist John Watson during 1924 when a new born child was considered to be a ‘tabula rasa’ or blank slate onto which anything could be sculpted.
In the 1980s, a New Zealand scientist, James Flynn, noticed that IQ was increasing at an average rate of about 3 IQ points per decade. There have been many theories for the Flynn effect, Ulric Neisser theorized that the Flynn effect was due to the way we are saturated with visual images such as ads, posters, video games and TV graphics. Neisser suggested that children experience a much richer visual environment than in the past and that this assists them in IQ tests.
Bouchard & Segal also supported the environmental view with their studies in 1985. Their results suggested that different circumstances have been found to vary IQ. Circumstances like the number of years spent in school, your father’s profession and ambition, average TV viewing and book-reading and the degree of personal self- confidence and authority in the parental home.
“No single environmental factor seems to have a large influence on IQ…most of the factors studied influence IQ in a direction.” (Bouchard & Segal, 1985).
Psychologist Wahlsten was praised for the high levels of control in his adoption studies in France. Wahlsten hypothesized that in order to raise IQ you would need to transfer a child born in a low socioeconomic home to a home of a higher socioeconomic group. The results proved his hypothesis showing a raise of 12 to 16 points (Wahlsten, 1997).
Several studies have demonstrated improvements in IQ by improving the lives of those disadvantaged (Gross, 2002). These studies selected families with low parental IQ and education with minimal financial resources. The families received educational day care outside the home every weekday from 3 months old till school age. Even though the children returned to their home environment every day there were sufficient differences in IQ between these experimental groups and the control families.
A criticism of educational enrichment studies is what are they actually testing? Is it an increased IQ or simply the ability to performance on a test? Children on these types of programs often received extensive practice in test-taking.
This would account for the fade-out effect, whereby the IQ is initially high but will return to the level of the control group a few years after the experiment. The Head Start program within the US aimed to enhance the schooling of disadvantaged children. On the whole, the results were mixed but in the end programs like this were criticized for not living up to expectations, in terms of changing IQ. The main defense for Head start was that its primary aim was not to improve IQ, but to accelerate academic development; IQ change was just a bonus.
Currently the psychological world is somewhere in between, both nature and nurture are seen as playing important roles. The view is more of an interactionist and best expressed by Ridley (Ridley, 1999).
“Mother Nature has plainly not entrusted the determination of our intellectual capacities to the blind fate of a gene or genes; she gave us parents, learning, language, culture and education to program ourselves with.”
It would appear that there are many psychological and biological factors each contributing a small fraction to the variance of intelligence. Our environment is partly a consequence of our genes but we create our own private environment, a bookworm will always seek out a book. I see it as genes create an appetite rather than an aptitude. Gene expression is environment dependent; one simply could not exist without the other.
A future area to research would be to blend the theories of both. Feldman suggested examining which environmental components allow people to realize their genetic potentials for a variety of areas of cognitive performance (Feldman, 1985).
Reference
Bouchard, T. J., & Segal, N. L. (1985) Environment and IQ – Intelligence: Theories, Measurements, and Applications, John Wiley, New York.
Ceci, S. J. (2001) Intelligence: The surprising truth, Psychology Today, July-August, 46-53.
Feldman, D. H. (1985) Nature’s Gambit: Child Prodigies and the Development of Human Potential, Basic Books, New York.
Galton, F. (2006) Hereditary Genius: Its Laws and Consequences, Prometheus Books, 3rd edition.
Gross, R. (2002) Psychology: The Science of Mind and Behaviour, Hodder and Stoughton Education, London.
Ridley, M. (1999) Genome: The autobiography of a species, London.
Swallow, C. (2009) Lessons notes – Unit 2.2 [online] available from: http://blackboard.nhc.ac.uk/webapps/portal/frameset.jsp?tab_id=_2_1&url=%2fwebapps%2fblackboard%2fexecute%2flauncher%3ftype%3dCourse%26id%3d_13380_1%26url%3d (accessed on 20/11/09)
Sternberg, R. J., & Grigorenko, E. (Eds.) (1997). Intelligence, heredity, and environment. Cambridge, UK: Cambridge University Press.
Wahlsten, D. (1997) The malleability of intelligence is not constrained by heritability, Springer, New York.
Winship, C., & Korenman, S. (1997). Does staying in school make you smarter? The effect of IQ in The Bell Curve, Springer, New York.
Mintys Mints 